How do you play as vemon in Spider-Man PS1?

You can't play as Venom in the original Spider-Man PS1 game. There is no playable Venom in the game, and he is only a boss character.

The game features a variety of villains like Green Goblin, Doctor Octopus, and the Shocker, but Venom is only encountered as a large, challenging boss fight.

While the game doesn't allow you to play as Venom, there have been other Spider-Man games that have included him as a playable character, such as the Spider-Man 2 game released in 2004.